From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752490AbZHABKx (ORCPT ); Fri, 31 Jul 2009 21:10:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751719AbZHABKw (ORCPT ); Fri, 31 Jul 2009 21:10:52 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:51690 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751368AbZHABKw (ORCPT ); Fri, 31 Jul 2009 21:10:52 -0400 Message-ID: <77df8765230d9f83859fde3119a2d60a.squirrel@webmail-b.css.fujitsu.com> In-Reply-To: References: <20090730180029.c4edcc09.kamezawa.hiroyu@jp.fujitsu.com> <20090730190216.5aae685a.kamezawa.hiroyu@jp.fujitsu.com> <20090731093305.50bcc58d.kamezawa.hiroyu@jp.fujitsu.com> <7f54310137837631f2526d4e335287fc.squirrel@webmail-b.css.fujitsu.com> Date: Sat, 1 Aug 2009 10:10:49 +0900 (JST) Subject: Re: [patch -mm v2] mm: introduce oom_adj_child From: "KAMEZAWA Hiroyuki" To: "David Rientjes" Cc: "KAMEZAWA Hiroyuki" , "Andrew Morton" , "Rik van Riel" , "Paul Menage" , "KOSAKI Motohiro" , linux-kernel@vger.kernel.org, linux-mm@kvack.org User-Agent: SquirrelMail/1.4.16 MIME-Version: 1.0 Content-Type: text/plain;charset=iso-2022-jp Content-Transfer-Encoding: 8bit X-Priority: 3 (Normal) Importance: Normal Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org David Rientjes wrote: >> > It livelocks if a thread is chosen and passed to oom_kill_task() while >> > another per-thread oom_adj value is OOM_DISABLE for a thread sharing >> the >> > same memory. >> > >> I say "why don't modify buggy selection logic?" >> >> Why we have to scan all threads ? >> As fs/proc/readdir does, you can scan only "process group leader". >> >> per-thread scan itself is buggy because now we have per-process >> effective-oom-adj. >> > > Without my patches to change oom_adj from task_struct to mm_struct, you'd > need to scan all tasks and not just the tgids because their oom_adj values > can differ amongst threads in the same thread group. So while it may now > be possible to shorten the scan as a result of my approach, it isn't a > solution itself to the problem. Did I said "revert your patch in -rc" even once ? livelock-avoidance itself is good work, thank you. All my suggestion is based on your patch already in rc4. Summarizing I think now ..... - rename mm->oom_adj as mm->effective_oom_adj - re-add per-thread oom_adj - update mm->effective_oom_adj based on per-thread oom_adj - if necessary, plz add read-only /proc/pid/effective_oom_adj file. or show 2 values in /proc/pid/oom_adj - rewrite documentation about oom_score. " it's calclulated from _process's_ memory usage and oom_adj of all threads which shares a memor context". This behavior is not changed from old implemtation, anyway. - If necessary, rewrite oom_kill itself to scan only thread group leader. It's a way to go regardless of vfork problem. > >> > How else do you propose the oom killer use oom_adj values on a >> per-thread >> > basis without considering other threads sharing the same memory? >> As I wrote. >> per-process(signal struct) or per-thread oom_adj and add >> mm->effecitve_oom_adj >> >> task scanning isn't necessary to do per-thread scan and you can scan >> only process-group-leader. What's bad ? >> If oom_score is problem, plz fix it to show effective_oom_score. >> > > When only using (and showing) mm->effective_oom_adj for a task, userspace > will not be able to adjust /proc/pid/oom_score with /proc/pid/oom_adj > as Documentation/filesystems/proc.txt says you can for a thread unless it > exceeds effective_oom_adj.> Is it different from old behavior ? I think documentation is wrong. It should say "you should think of multi-thread effect to oom_adj/oom_score". Thanks, -Kame > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >